I’m looking to find someone with a head ported by the Yoshimura company in the 70-80s. Cb750 head preferable, but others OK too. I’m looking to see the style of porting they incorporated, specifically “valve guide out” porting or “valve guide in” porting.

george, pics are better than nothing but honestly, seek someone who can make silicon castings... see attached pdf.im working quite a bit on the subject and exact shape and dimensions are super important for flow numbers, nearly impossible to judge from port pics

I totally agree, I am first trying to identify the porting styles in general and more specifically whether the particular cb750 head I have was plausibly ported by Yoshimura as was suggested possible by the seller(as 3rd owner of engine, 1st owner reportedly spent a pile with Yoshimura in the mid 70s, it had a hand bent Yoshimura stove pipe race exhaust and a set of Smoothbores 29s on it at the time that Ted (Ricky Racer) has kept.

Knowing whether Yoshimura stamped the parts they modified would be a great help too. That was common back then(RC Engineering, etc)